libcore: Add missing unit.rs

Author: pcwalton

src/libcore/unit.rs

@@ -0,0 +1,17 @@
+/**
+ * Functions for the unit type.
+ */
+
+use cmp::{Eq, Ord};
+
+impl () : Eq {
+    pure fn eq(&&_other: ()) -> bool { true }
+}
+
+impl () : Ord {
+    pure fn lt(&&_other: ()) -> bool { false }
+    pure fn le(&&_other: ()) -> bool { true }
+    pure fn ge(&&_other: ()) -> bool { true }
+    pure fn gt(&&_other: ()) -> bool { false }
+}
+